As Verizon, Sprint, T-Mobile and others work to bolster their cellular networks in the heart of the Big Apple, they are now facing another competitor: New York City, which this week began offering public access to its small but growing network of LinkNYC-branded public Wi-Fi hotspots.

Importantly, the city’s new network, which is being deployed by city officials and a consortium of companies called CityBridge, uses an underground network of fiber-optic cables that connect to Wi-Fi access points. The result, according to a handful of testers, is lightning fast connection speeds at 70 Mbps or higher. LinkNYC promised to deploy over 7,500 free, ad-supported Wi-Fi hotspots across the city’s five boroughs over the next several years.

As the Wall Street Journal notes, the city’s new Wi-Fi network supports Passpoint roaming technology, also called Hotspot 2.0. Passpoint allows Wi-Fi users to automatically connect to Passpoint hotspots, and to roam through those connections without having to log in at each hotspot. The combination of free, speedy public Wi-Fi and simple roaming could siphon users away from the cellular carriers that have spent billions of dollars purchasing spectrum and building networks to cover New York City.